Computer networks are used in many types of organisation, for example within business, industrial and educational organisations. A computer network typically comprises a number of computer systems interconnected by data communications links. Computer networks allow data to be shared between users of individual organisations, and also between users of different organisations.
Computer systems connected to such computer networks operate using software executed on the systems. Such software may contain vulnerabilities which render the software, and computer systems running the software, susceptible to interference by unauthorised means. As will be appreciated by those skilled in the art, a software vulnerability may be considered a feature of that software which renders it susceptible to processing operations not intended to be permitted or performed by that software. Examples of software vulnerabilities include features that enable malicious mobile code, e.g. computer viruses, to access and/or manipulate the software. Examples of well-known computer viruses are so-called ‘worms’ (which exploit software vulnerabilities and propagate through computer networks), and self-contained virus programs which usually require execution before any unwanted processing results.
Since computer networks facilitate the transfer of data across a large number of computer systems in a relatively short space of time, computer viruses, and especially worms-type viruses, can rapidly propagate across large network areas. The costs involved in remedying ‘infected’ systems can be very large and it is important that viruses are identified and mitigated as soon as possible so that their ability to spread across networks is limited.
A computer system which is arranged to slow down the spread of a computer virus is known. This conventional computer system operates by slowing the data connection between itself and any other computer which attempts to send it a computer virus.